<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
 <head>
  <meta http-equiv="content-type" content="text/html; charset=UTF-8">
  <title>指数表达式</title>
<link media="all" rel="stylesheet" type="text/css" href="styles/03e73060321a0a848018724a6c83de7f-theme-base.css" />
<link media="all" rel="stylesheet" type="text/css" href="styles/03e73060321a0a848018724a6c83de7f-theme-medium.css" />

 </head>
 <body class="docs"><div class="navbar navbar-fixed-top">
  <div class="navbar-inner clearfix">
    <ul class="nav" style="width: 100%">
      <li style="float: left;"><a href="function.pi.html">« pi</a></li>
      <li style="float: right;"><a href="function.rad2deg.html">rad2deg »</a></li>
    </ul>
  </div>
</div>
<div id="breadcrumbs" class="clearfix">
  <ul class="breadcrumbs-container">
    <li><a href="index.html">PHP Manual</a></li>
    <li><a href="ref.math.html">Math 函数</a></li>
    <li>指数表达式</li>
  </ul>
</div>
<div id="layout">
  <div id="layout-content"><div id="function.pow" class="refentry">
 <div class="refnamediv">
  <h1 class="refname">pow</h1>
   <p class="verinfo">(PHP 4, PHP 5, PHP 7, PHP 8)</p><p class="refpurpose"><span class="refname">pow</span> &mdash; <span class="dc-title">指数表达式</span></p>

 </div>
 <div class="refsect1 description" id="refsect1-function.pow-description">
  <h3 class="title">说明</h3>
   <div class="methodsynopsis dc-description">
   <span class="methodname"><strong>pow</strong></span>(<span class="methodparam"><span class="type"><a href="language.types.declarations.html#language.types.declarations.mixed" class="type mixed">mixed</a></span> <code class="parameter">$num</code></span>, <span class="methodparam"><span class="type"><a href="language.types.declarations.html#language.types.declarations.mixed" class="type mixed">mixed</a></span> <code class="parameter">$exponent</code></span>): <span class="type"><span class="type">int</span>|<span class="type">float</span>|<span class="type">object</span></span></div>

  <p class="para rdfs-comment">
   返回 <code class="parameter">num</code> 的 <code class="parameter">exponent</code> 次方的幂。
  </p>
  <blockquote class="note"><p><strong class="note">注意</strong>: 
   <p class="para">
    可以使用 <a href="language.operators.arithmetic.html" class="link">**</a> 运算符代替。
   </p>
  </p></blockquote>
 </div>

 <div class="refsect1 parameters" id="refsect1-function.pow-parameters">
  <h3 class="title">参数</h3>
  <p class="para">
   <dl>
    
     <dt>
<code class="parameter">num</code></dt>

     <dd>

      <p class="para">
       底数
      </p>
     </dd>

    
    
     <dt>
<code class="parameter">exponent</code></dt>

     <dd>

      <p class="para">
       指数
      </p>
     </dd>

    
   </dl>

  </p>
 </div>

 <div class="refsect1 returnvalues" id="refsect1-function.pow-returnvalues">
  <h3 class="title">返回值</h3>
  <p class="para">
   <code class="parameter">num</code> 的 <code class="parameter">exponent</code>
   次方。如果两个参数都是非负整数且结果可以用整数表示，则返回 <span class="type">int</span>
   类型，否则返回 <span class="type">float</span>。
  </p>
 </div>

 <div class="refsect1 examples" id="refsect1-function.pow-examples">
  <h3 class="title">范例</h3>
  <p class="para">
   <div class="example" id="example-3103">
    <p><strong>示例 #1 <span class="function"><strong>pow()</strong></span> 的一些例子</strong></p>
    <div class="example-contents">
<div class="phpcode"><code><span style="color: #000000">
<span style="color: #0000BB">&lt;?php<br /><br />var_dump</span><span style="color: #007700">(</span><span style="color: #0000BB">pow</span><span style="color: #007700">(</span><span style="color: #0000BB">2</span><span style="color: #007700">,&nbsp;</span><span style="color: #0000BB">8</span><span style="color: #007700">));&nbsp;</span><span style="color: #FF8000">//&nbsp;int(256)<br /></span><span style="color: #007700">echo&nbsp;</span><span style="color: #0000BB">pow</span><span style="color: #007700">(-</span><span style="color: #0000BB">1</span><span style="color: #007700">,&nbsp;</span><span style="color: #0000BB">20</span><span style="color: #007700">);&nbsp;</span><span style="color: #FF8000">//&nbsp;1<br /></span><span style="color: #007700">echo&nbsp;</span><span style="color: #0000BB">pow</span><span style="color: #007700">(</span><span style="color: #0000BB">0</span><span style="color: #007700">,&nbsp;</span><span style="color: #0000BB">0</span><span style="color: #007700">);&nbsp;</span><span style="color: #FF8000">//&nbsp;1<br /></span><span style="color: #007700">echo&nbsp;</span><span style="color: #0000BB">pow</span><span style="color: #007700">(</span><span style="color: #0000BB">10</span><span style="color: #007700">,&nbsp;-</span><span style="color: #0000BB">1</span><span style="color: #007700">);&nbsp;</span><span style="color: #FF8000">//&nbsp;0.1<br /><br /></span><span style="color: #007700">echo&nbsp;</span><span style="color: #0000BB">pow</span><span style="color: #007700">(-</span><span style="color: #0000BB">1</span><span style="color: #007700">,&nbsp;</span><span style="color: #0000BB">5.5</span><span style="color: #007700">);&nbsp;</span><span style="color: #FF8000">//&nbsp;NAN<br /></span><span style="color: #0000BB">?&gt;</span>
</span>
</code></div>
    </div>

   </div>
  </p>
 </div>


 <div class="refsect1 notes" id="refsect1-function.pow-notes">
  <h3 class="title">注释</h3>
  <blockquote class="note"><p><strong class="note">注意</strong>: 
   <p class="para">
    本函数会转换所有输入为数字，甚至是非标量值，将会导致<code class="literal">怪异的</code>结果。
   </p>
  </p></blockquote>
 </div>


 <div class="refsect1 seealso" id="refsect1-function.pow-seealso">
  <h3 class="title">参见</h3>
  <p class="para">
   <ul class="simplelist">
    <li class="member"><span class="function"><a href="function.exp.html" class="function" rel="rdfs-seeAlso">exp()</a> - 计算 e 的指数</span></li>
    <li class="member"><span class="function"><a href="function.sqrt.html" class="function" rel="rdfs-seeAlso">sqrt()</a> - 平方根</span></li>
    <li class="member"><span class="function"><a href="function.bcpow.html" class="function" rel="rdfs-seeAlso">bcpow()</a> - 任意精度数字的乘方</span></li>
    <li class="member"><span class="function"><a href="function.gmp-pow.html" class="function" rel="rdfs-seeAlso">gmp_pow()</a> - Raise number into power</span></li>
   </ul>
  </p>
 </div>

</div></div></div></body></html>